1. Field of the Invention
The present invention relates generally to an in-line and multi-chamber sputtering process of vacuum deposition system, and more particularly to a self-adjustable and cross-chamber transmission system.
2. Description of the Related Art
FIG. 1 shows the flow chart of the in-line sputtering process. FIG. 2 is a sketch diagram of the conventional sputter system, which is consisted at least a load chamber 50, a sputter chamber 52 for reactive magnetron sputtering process, and an unload chamber 54. Because the vacuum requirements of sputtering process, prior to the sputtering procedure a vacuum of less than one ten millionth of an atmosphere must be achieved. Gates 56 are provided between the chambers 50, 52, and 54 for isolation with the neighboring chambers. According to the quality requirement of sputtering, more modular sub-chambers can be added to the system for pre-treatment and post-treatment of gradient vacuum conditions. These additional sub-chambers are used to achieve the required vacuum and clearance requirements gradually. Each chamber has an independent transmission device therein (not shown in FIG. 2) to transport a carrier 14, on which the substrate is rested, crossing the chambers. The conventional transmission device includes a plurality of parallel shafts pivoted on a bottom of the chamber. To achieve a real-time and synchronous motion, the shafts are connected with each other by chains or teeth belts and are driven by a motor. A carrier, on which substrates are placed, is rested on the shafts for transport from the front chamber to the next. A limit switch and a PLC controller are provided to control the motion process of the carrier crossing the chambers, and the open/close process of the gates.
For the isolation of the gates 56, the conventional transmission device applied the friction force between the shafts and the carrier to transport the carrier crossing the chambers. However, the skid and slip may be occurred on the carrier because of insufficient friction or unequal distribution of friction. Typically, the shafts are provided and installed with plastic O-rings at both sides to increase the friction coefficient. However, the O-rings will be worn gradually during transport process. After some time, the dust and particles of the O-rings are deposited in the chamber and on a bottom of the transmission device. In the sputtering process, the dust and particles will be diffused in the vacuum condition and then pollute the cleanness of the chamber. It will cause unusual convexity or exceptional penetrability. Not only the bonding force and uniformity of the coating surfaces, but also the optical characteristics and electrical functions of the products are affected. As a result, the conventional sputtering system needs to shut down periodically for clearing the dust on the surfaces of the chamber and the transmission device after a predetermined time. It decreases the activation and the efficiency of the system. Moreover, the deposited dust and particles produced by wear and abrasion can't be avoided for the conventional transmission device, and the impractical operation of clearing still can't completely prevent the system from the above drawbacks. Moreover, the unequal friction distribution of the shafts at both sides may cause unexpected skew or tremulous motion, and hence result in instability of the transport.